Don Cuevas, I'm curious about Restaurante La Cabaña del Lago. I haven't heard about it and it sounds worth a try.
A couple of years ago, some friends took my wife and I to a Talapia Farm on the lake where they had a small restaurant that served every manner of talapia. It was great and inexpensive. Unfortunately, it was hard to find and I don't even have a name nor any good way to find it (except that I "saved" the location on my car GPS). It is almost exactly on the opposite side of the lake from Cuitzeo.